We continue our development of carbon monoxide (CO)-monitoring technology for laboratory and bedside diagnosis of hemolysis or increased total bilirubin production from other causes. This involves developing and refining instrumentation and techniques for noninvasive diagnosis of hemolysis at the bedside through measurement of excreted CO. We have developed an automatic sampler for this purpose and used them successfully in a multi-center NICHD study. However, even though the sampler consistently sampled neonatal breath, its efficiency was only 60 + 12% and the CO was found to have sensor specific sensitivity to H2, a prominent compound in the breath of neonates with colonized intestines. It is essential to eliminate this source of error.